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Heating - Solar water heater - Swimming pool - Indoor / Canada (Guelph)
Case study assignment
The city of Kitchener, Ontario is interested in using renewable energy to reduce natural gas consumption at its community centre. The city has asked you to assess the feasibility of installing a solar water heating (SWH) system to offset a portion of the annual energy required to heat the indoor swimming pool at the centre.
Site information
The community centre is located in the city of Kitchener, which is about 100 km west of Toronto. The closest appropriate weather station is in Guelph, Ontario. The community centre was built in the 1960's and uses natural gas to heat an indoor pool. The seasonal efficiency of the pool-heating boiler is 75%. The pool has an area of 244 m² exposed to the indoor air. The manager of the pool does not allow a pool cover to be used due to safety regulations. The desired temperature for the pool is 29°C and 5% of the pool water is replaced every week.
The community centre building is large with a flat roof and can accommodate more than 100 collectors facing due south at any slope. Typically the collectors' optimal slope for year-round operation at this latitude is between 30° and 40°, however the collectors are to be sloped at 45° to improve snow shedding in the winter.
The city has requested that you use NORSUN model TD-3000-30 glazed collectors in your analysis. These collectors have an area of 3 m² each, an Fr (tau alpha) coefficient of 0.68 and an Fr UL coefficient of 3.62 (W/m²)/°C. The city also wants the collectors to be arranged in four equal sized sub-arrays for aesthetic reasons. Pool water will be circulated directly through the collectors (i.e. no heat exchanger required). The water in the collectors and piping will drain back to the pool when the pump deactivates. Based on previous experience with similar systems, pumping power is expected to be 5 W/m². The horizontal distance from the mechanical room to the collectors is 20 m and the collectors are 3 floors above the mechanical room.
For the greenhouse gas (GHG) emissions reduction calculation, assume that natural gas is the fuel displaced at the margin for electricity generation in Ontario.
Financial information
An engineering feasibility study for the project will cost $2,500 and the engineering design will cost an additional $7,500. The NORSUN collectors cost $280/m² and the support structure required to mount the collectors to the roof will cost $150/m² of collector. The installation of the collectors is expected to cost $100/m² of collector.
If the project is approved by city council, the community centre will purchase the system without any financing. The current cost of natural gas for the centre is approximately $0.35/m³ and the current cost of electricity is approximately $0.10/kWh. The fuel cost escalation rate is uncertain but on average is expected to be 4% per year. The inflation rate is expected to be uniform at approximately 2% per year. The discount rate used for the analysis should be 9%. The expected service life of the installed equipment is 30 years with an annual maintenance cost of $500/year.
Please note that the project is eligible for a federal government incentive that will provide a refund of 25% of the purchase and installation costs of the system, up to a maximum refund of $80,000.
Prepare a RETScreen study (including greenhouse gas emission reduction analysis) to determine the feasibility of the project. Document any assumptions that you are required to make and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
Real project
Results
The Breithaupt Community Centre in the city of Kitchener, Ontario (about 100 km west of Toronto) installed a solar water heating (SWH) system for its indoor pool over 20 years ago. The system has operated reliably since it was commissioned and has reduced the use of a conventional natural gas-fired boiler. Service technicians working for the city indicate that it provides a substantial amount of the heat required for the pool and that they are satisfied with the system.
System description
The solar water heating system consists of 80 NORSUN flat-plate, heat pipe collectors. The total array is divided into 4 equal size sub-arrays. The collectors face due south and are mounted at an angle of approximately 45°.
When the sun is shining and the pool requires heat, pool water from a small holding reservoir (connected to the pool) is pumped up from the mechanical room to the collectors on the roof. The total flow is divided into two parallel streams, each passing through 2 of the 4 sub-arrays (i.e. 40 heat pipe collectors in series). The heated water then returns to the mechanical room where it is supplied to the pool. Pool water is circulated directly through the collectors without the use of a heat exchanger. Freeze protection is provided by allowing the water in the collectors and piping to drain back to the pool when the pump deactivates.
Lessons learned
The big picture
Public swimming pools are particularly attractive applications for solar water heating systems. Large heating loads throughout the year (to maintain comfortable pool temperatures) and high energy rates result in large heating bills for pool operators. Solar water heating systems can deliver excellent performance, reliability and longevity and can significantly offset the use of conventional energy sources such as natural gas that contribute to greenhouse gas emissions.
Photo
Recreation centre - Swimming pool - Indoor - Solar water heater, Ontario, Canada
References
Case study assignment
The city of Kitchener, Ontario is interested in using renewable energy to reduce natural gas consumption at its community centre. The city has asked you to assess the feasibility of installing a solar water heating (SWH) system to offset a portion of the annual energy required to heat the indoor swimming pool at the centre.
Site information
The community centre is located in the city of Kitchener, which is about 100 km west of Toronto. The closest appropriate weather station is in Guelph, Ontario. The community centre was built in the 1960's and uses natural gas to heat an indoor pool. The seasonal efficiency of the pool-heating boiler is 75%. The pool has an area of 244 m² exposed to the indoor air. The manager of the pool does not allow a pool cover to be used due to safety regulations. The desired temperature for the pool is 29°C and 5% of the pool water is replaced every week.
The community centre building is large with a flat roof and can accommodate more than 100 collectors facing due south at any slope. Typically the collectors' optimal slope for year-round operation at this latitude is between 30° and 40°, however the collectors are to be sloped at 45° to improve snow shedding in the winter.
The city has requested that you use NORSUN model TD-3000-30 glazed collectors in your analysis. These collectors have an area of 3 m² each, an Fr (tau alpha) coefficient of 0.68 and an Fr UL coefficient of 3.62 (W/m²)/°C. The city also wants the collectors to be arranged in four equal sized sub-arrays for aesthetic reasons. Pool water will be circulated directly through the collectors (i.e. no heat exchanger required). The water in the collectors and piping will drain back to the pool when the pump deactivates. Based on previous experience with similar systems, pumping power is expected to be 5 W/m². The horizontal distance from the mechanical room to the collectors is 20 m and the collectors are 3 floors above the mechanical room.
For the greenhouse gas (GHG) emissions reduction calculation, assume that natural gas is the fuel displaced at the margin for electricity generation in Ontario.
Financial information
An engineering feasibility study for the project will cost $2,500 and the engineering design will cost an additional $7,500. The NORSUN collectors cost $280/m² and the support structure required to mount the collectors to the roof will cost $150/m² of collector. The installation of the collectors is expected to cost $100/m² of collector.
If the project is approved by city council, the community centre will purchase the system without any financing. The current cost of natural gas for the centre is approximately $0.35/m³ and the current cost of electricity is approximately $0.10/kWh. The fuel cost escalation rate is uncertain but on average is expected to be 4% per year. The inflation rate is expected to be uniform at approximately 2% per year. The discount rate used for the analysis should be 9%. The expected service life of the installed equipment is 30 years with an annual maintenance cost of $500/year.
Please note that the project is eligible for a federal government incentive that will provide a refund of 25% of the purchase and installation costs of the system, up to a maximum refund of $80,000.
Prepare a RETScreen study (including greenhouse gas emission reduction analysis) to determine the feasibility of the project. Document any assumptions that you are required to make and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
- The temperature of the incoming cold water (makeup water) is not known so it is set to "Auto" to let the model calculate it based on air temperature throughout the year.
- To achieve four equal sized sub-arrays, the number of collectors is dropped from the recommended 82 to 80.
- A heat exchanger is not used, so "Heat Exchanger/antifreeze protection" is set to "No". However, the system does drain-back for freeze protection. Alternatively, setting "Heat Exchanger/antifreeze protection" to "Yes" (to indicate that freeze protection exists) and setting the heat exchanger effectiveness to 100% will yield the same results.
- A relatively high cost of $3000 was included to allow for delivery of the equipment to the location since glazed collectors are heavy and cumbersome.
- There are no credits for the system because a conventional heater is already installed.
Real project
Results
The Breithaupt Community Centre in the city of Kitchener, Ontario (about 100 km west of Toronto) installed a solar water heating (SWH) system for its indoor pool over 20 years ago. The system has operated reliably since it was commissioned and has reduced the use of a conventional natural gas-fired boiler. Service technicians working for the city indicate that it provides a substantial amount of the heat required for the pool and that they are satisfied with the system.
System description
The solar water heating system consists of 80 NORSUN flat-plate, heat pipe collectors. The total array is divided into 4 equal size sub-arrays. The collectors face due south and are mounted at an angle of approximately 45°.
When the sun is shining and the pool requires heat, pool water from a small holding reservoir (connected to the pool) is pumped up from the mechanical room to the collectors on the roof. The total flow is divided into two parallel streams, each passing through 2 of the 4 sub-arrays (i.e. 40 heat pipe collectors in series). The heated water then returns to the mechanical room where it is supplied to the pool. Pool water is circulated directly through the collectors without the use of a heat exchanger. Freeze protection is provided by allowing the water in the collectors and piping to drain back to the pool when the pump deactivates.
Lessons learned
- The system has operated reliably since it was installed over 20 years ago. This demonstrates the longevity possible with well designed renewable energy systems.
- The application of solar water heating to indoor swimming pools is reasonable alternative given the high heating costs associated with pools and the good performance, reliability and longevity of well designed solar water heating systems.
The big picture
Public swimming pools are particularly attractive applications for solar water heating systems. Large heating loads throughout the year (to maintain comfortable pool temperatures) and high energy rates result in large heating bills for pool operators. Solar water heating systems can deliver excellent performance, reliability and longevity and can significantly offset the use of conventional energy sources such as natural gas that contribute to greenhouse gas emissions.
Photo
Recreation centre - Swimming pool - Indoor - Solar water heater, Ontario, Canada
References
- Dent, Ed, "Personal communication," City of Kitchener, 2002.
- McLennan, Rob, "Personal communication," City of Kitchener, 2002.
- Pelton, Michael, "Personal communication," Enermodal Engineering Ltd., 2002.
